<template>
  <div class="slider" ref="slider">
    <div class="slider-group" ref="sliderGroup">
      <slot></slot>
    </div>
    <div class="dots">
      <span
        class="dot"
        v-for="(item, index) in dots"
        :key="index"
        :class="{active: currentPageIndex === index}"
      >{{item}}</span>
    </div>
  </div>
</template>
<script type="text/ecmascript-6">
import BScroll from 'better-scroll'
import { addClass } from 'common/js/dom.js'
export default {
  data() {
    return {
      dots: [],
      currentPageIndex: 0
    }
  },
  props: {
    loop: {
      type: Boolean,
      default: true
    },
    autoPlay: {
      type: Boolean,
      default: true
    },
    interval: {
      type: Number,
      default: 4000
    }
  },
  mounted() {
    setTimeout(() => {
      this._setSliderWidth()
      this._initDots()
      this._initSlider()

      if (this.autoPlay) {
        this._paly()
      }
    }, 20)
    window.addEventListener('resize', () => {
      if (!this.slider) {
        return false
      }
      this._setSliderWidth(true)
      this.slider.refresh()// 重新调整图片大小时刷新slider实例
    })
  },
  methods: {
    _setSliderWidth(isResize) {
      this.children = this.$refs.sliderGroup.children// 初始化如果是5个，当window变化时重新调用此函数

      let width = 0
      let sliderWidth = this.$refs.slider.clientWidth
      for (var i = 0; i < this.children.length; i++) {
        let child = this.children[i]
        addClass(child, 'slider-item')

        child.style.width = sliderWidth + 'px'
        width += sliderWidth
      }
      if (this.loop && !isResize) {
        width += 2 * sliderWidth//  better-scroll插件的loop 需要再加两个长度
      }
      this.$refs.sliderGroup.style.width = width + 'px'
    },
    _initDots() {
      this.dots = new Array(this.children.length)
    },
    _initSlider() {
      this.slider = new BScroll(this.$refs.slider, {
        scrollX: true,
        scrollY: false,
        momentum: false, // 惯性
        snap: {
          loop: this.loop, // 循环
          threshold: 0.3,
          speed: 400 // 轮播间隔
        },
        click: true
      })
      // console.log(this)
      this.slider.on('scrollEnd', () => {
        let pageIndex = this.slider.getCurrentPage().pageX
        if (this.loop) {
          // pageIndex -= 1
        }
        this.currentPageIndex = pageIndex
        if (this.autoPlay) {
          clearTimeout(this.timer)
          this._paly()
        }
      })
    },
    _paly() {
      let pageIndex = this.currentPageIndex
      if (this.loop) {
        pageIndex += 1
      }
      // console.log(this.currentPageIndex)
      if (pageIndex === this.children.length - 2) {
        pageIndex = 0
      }
      this.timer = setTimeout(() => {
        this.slider.goToPage(pageIndex, 0, 400)
      }, this.interval)
    }
  },
  destroyed() {
    clearTimeout(this.timer)
  }
}
</script>
<style scoped lang="stylus" rel="stylesheet/stylus">
@import '~common/stylus/variable';

.slider {
  min-height: 1px;

  .slider-group {
    position: relative;
    overflow: hidden;
    white-space: nowrap;

    .slider-item {
      float: left;
      box-sizing: border-box;
      overflow: hidden;
      text-align: center;

      a {
        display: block;
        width: 100%;
        overflow: hidden;
        text-decoration: none;
      }

      img {
        display: block;
        width: 100%;
      }
    }
  }

  .dots {
    position: absolute;
    right: 0;
    left: 0;
    bottom: 12px;
    text-align: center;
    font-size: 0;

    .dot {
      display: inline-block;
      margin: 0 4px;
      width: 8px;
      height: 8px;
      border-radius: 50%;
      background: $color-text-l;

      &.active {
        width: 20px;
        border-radius: 5px;
        background: $color-text-ll;
      }
    }
  }
}
</style>
